PROGRAM STATEMENT
Design a super class called Staff with details as StaffId, Name, Phone, Salary. Extend this class by writing three subclasses namely Teaching (domain, publications), Technical (skills), and Contract (period). Write a Java program to read and display at least 3 staff objects of all three categories.
CONCEPT
Here in this given problem we shall use inheritance for extending Staff class into Teaching, Technical and Contract 3 subclasses using extends keyword. Each class is having the variables as given in the bracket. We will import the util package Scanner class to read 3 objects of each class. Create a constructor of Staff class to initialize StaffId, Name, Phone, Salary. And one display functions into the Staff class to display the entered values. All the data members of Staff will be inherited in Teaching, Technical and Contract using the super keyword that calls the superclass constructor to the base class. Other additional data members of the subclasses would be initialized using their own constructor. Also along with their own constructors, all 3 subclasses will have their own display method that invokes display method of super class Staff. Now in main() method using Scanner class we will read the values accordingly. To display these values we will create an array of object of size 3 for each subclass Teaching, Technical and Contract. Using this array of objects we will display the values entered previously by invoking display method of each subclass. Below is the program that demonstrates the same.
EXAMPLE INHERITANCE IN JAVA (SUPER CLASS / SUBCLASS) PROGRAM
/** Design a super class called Staff with details as StaffId, Name, Phone, Salary. Extend this class by writing three subclasses namely Teaching (domain, publications), Technical (skills), and Contract (period). Write a Java program to read and display at least 3 staff objects of all three categories.*/
package daa.EXP2AB; import java.util.Scanner; class Staff { //data members of Staff class String StaffId=null, Name=null, Phone=null; float Salary; //constructor to initialize Staff class data members Staff(String S,String N,String P,float Sa) { StaffId=S; Name=N; Phone=P; Salary=Sa; } //display method to display the data members public void display() { System.out.println("Entered Details are:"); System.out.println("StaffID:"+StaffId); System.out.println("Name:"+Name); System.out.println("Phone:"+Phone); System.out.println("Salary:"+Salary); } } //Subclass of Staff class Teaching extends Staff { //data members of Teaching class String domain=null, publications=null; public Teaching(String S, String N, String P, float Sa,String d,String p) { //super invokes super class Staff constructor super(S, N, P, Sa); domain=d; publications=p; } public void display() { //super invokes display super class method super.display(); System.out.println("Domain:"+domain); System.out.println("Publication:"+publications); } } class Technical extends Staff { String skills=null; public Technical(String S, String N, String P, float Sa,String Sk) { //super invokes Staff super class constructor super(S, N, P, Sa); skills=Sk; } public void display() { //super invokes display super class method super.display(); System.out.println("Skills:"+skills); } } class Contract extends Staff { float period;//in years public Contract(String S, String N, String P, float Sa,float p) { super(S, N, P, Sa); period=p; } public void display() { //super invokes display super class method super.display(); System.out.println("Period:"+period); } } public class StaffDemo { public static void main(String args[]) { Scanner s = new Scanner(System.in); String StaffId[]=new String[3]; String Name[]=new String[3]; String Phone[]=new String[3]; float Salary[]=new float[3]; String Domain[]=new String[3]; String Publications[]=new String[3]; System.out.println("Enter the Details for Teachers"); for(int i=0;i<3;i++) { //reading variables of Staff System.out.println("Enter StaffId"); StaffId[i] = s.next(); System.out.println("Enter Name"); Name[i] = s.next(); System.out.println("Enter Phone"); Phone[i] = s.next(); System.out.println("Enter Salary"); Salary[i] = s.nextFloat(); //reading variables of Teaching System.out.println("Enter Domain"); Domain[i] = s.next(); System.out.println("Enter Publications"); Publications[i] = s.next(); } //Dislaying variables of Teaching Teaching T1[]=new Teaching[3]; for(int k=0;k<3;k++) { T1[k]=new Teaching(StaffId[k],Name[k],Phone[k],Salary[k],Domain[k],Publications[k]); T1[k].display(); } Scanner s2 = new Scanner(System.in); String StaffIdT[]=new String[3]; String NameT[]=new String[3]; String PhoneT[]=new String[3]; float SalaryT[]=new float[3]; String Skills[]=new String[3]; System.out.println("Enter the Details for Technical"); for(int j=0;j<3;j++) { //reading variables of Staff System.out.println("Enter StaffId"); StaffIdT[j] = s2.next(); System.out.println("Enter Name"); NameT[j] = s2.next(); System.out.println("Enter Phone"); PhoneT[j] = s2.next(); System.out.println("Enter Salary"); SalaryT[j] = s2.nextFloat(); //reading variables of Technical System.out.println("Enter Skills"); Skills[j] = s2.next(); } //Dislaying variables of Technical Technical Te1[]=new Technical[3]; for(int x=0;x<3;x++) { Te1[x]=new Technical(StaffIdT[x],NameT[x],PhoneT[x],SalaryT[x],Skills[x]); Te1[x].display(); } Scanner s3 = new Scanner(System.in); String StaffIdC[]=new String[3]; String NameC[]=new String[3]; String PhoneC[]=new String[3]; float SalaryC[]=new float[3]; float period[]=new float[3]; System.out.println("Enter the Details for Contract"); for(int k=0;k<3;k++) { //reading variables of Staff System.out.println("Enter StaffId"); StaffIdC[k] = s3.next(); System.out.println("Enter Name"); NameC[k] = s3.next(); System.out.println("Enter Phone"); PhoneC[k] = s3.next(); System.out.println("Enter Salary"); SalaryC[k] = s3.nextFloat(); //reading variables of Contract System.out.println("Enter Period"); period[k] = s3.nextFloat(); } //Dislaying variables of Contract Contract C1[]=new Contract[3]; for(int y=0;y<3;y++) { C1[y]=new Contract(StaffIdC[y],NameC[y],PhoneC[y],SalaryC[y],period[y]); C1[y].display(); } } }
OUTPUT
Output of JAVA Inheritance